@phdthesis{Schuck2020,
  author    = {Schuck, Bernhard},
  title     = {Geomechanical and petrological characterisation of exposed slip zones, Alpine Fault, New Zealand},
  doi       = {10.25932/publishup-44612},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-446129},
  school      = {Universit{\"a}t Potsdam},
  pages     = {XVII, 143},
  year      = {2020},
  abstract  = {The Alpine Fault is a large, plate-bounding, strike-slip fault extending along the north-western edge of the Southern Alps, South Island, New Zealand. It regularly accommodates large (MW > 8) earthquakes and has a high statistical probability of failure in the near future, i.e., is late in its seismic cycle. This pending earthquake and associated co-seismic landslides are expected to cause severe infrastructural damage that would affect thousands of people, so it presents a substantial geohazard. The interdisciplinary study presented here aims to characterise the fault zone's 4D (space and time) architecture, because this provides information about its rheological properties that will enable better assessment of the hazard the fault poses. The studies undertaken include field investigations of principal slip zone fault gouges exposed along strike of the fault, and subsequent laboratory analyses of these outcrop and additional borehole samples. These observations have provided new information on (I) characteristic microstructures down to the nanoscale that indicate which deformation mechanisms operated within the rocks, (II) mineralogical information that constrains the fault's geomechanical behaviour and (III) geochemical compositional information that allows the influence of fluid- related alteration processes on material properties to be unraveled. Results show that along-strike variations of fault rock properties such as microstructures and mineralogical composition are minor and / or do not substantially influence fault zone architecture. They furthermore provide evidence that the architecture of the fault zone, particularly its fault core, is more complex than previously considered, and also more complex than expected for this sort of mature fault cutting quartzofeldspathic rocks. In particular our results strongly suggest that the fault has more than one principal slip zone, and that these form an anastomosing network extending into the basement below the cover of Quaternary sediments. The observations detailed in this thesis highlight that two major processes, (I) cataclasis and (II) authigenic mineral formation, are the major controls on the rheology of the Alpine Fault. The velocity-weakening behaviour of its fault gouge is favoured by abundant nanoparticles promoting powder lubrication and grain rolling rather than frictional sliding. Wall-rock fragmentation is accompanied by co-seismic, fluid-assisted dilatancy that is recorded by calcite cementation. This mineralisation, along with authigenic formation of phyllosilicates, quickly alters the petrophysical fault zone properties after each rupture, restoring fault competency. Dense networks of anastomosing and mutually cross-cutting calcite veins and intensively reworked gouge matrix demonstrate that strain repeatedly localised within the narrow fault gouge. Abundantly undeformed euhedral chlorite crystallites and calcite veins cross-cutting both fault gouge and gravels that overlie basement on the fault's footwall provide evidence that the processes of authigenic phyllosilicate growth, fluid-assisted dilatancy and associated fault healing are processes active particularly close to the Earth's surface in this fault zone. Exposed Alpine Fault rocks are subject to intense weathering as direct consequence of abundant orogenic rainfall associated with the fault's location at the base of the Southern Alps. Furthermore, fault rock rheology is substantially affected by shallow-depth conditions such as the juxtaposition of competent hanging wall fault rocks on poorly consolidated footwall sediments. This means microstructural, mineralogical and geochemical properties of the exposed fault rocks may differ substantially from those at deeper levels, and thus are not characteristic of the majority of the fault rocks' history. Examples are (I) frictionally weak smectites found within the fault gouges being artefacts formed at temperature conditions, and imparting petrophysical properties that are not typical for most of fault rocks of the Alpine Fault, (II) grain-scale dissolution resulting from subaerial weathering rather than deformation by pressure-solution processes and (III) fault gouge geometries being more complex than expected for deeper counterparts. The methodological approaches deployed in analyses of this, and other fault zones, and the major results of this study are finally discussed in order to contextualize slip zone investigations of fault zones and landslides. Like faults, landslides are major geohazards, which highlights the importance of characterising their geomechanical properties. Similarities between faults, especially those exposed to subaerial processes, and landslides, include mineralogical composition and geomechanical behaviour. Together, this ensures failure occurs predominantly by cataclastic processes, although aseismic creep promoted by weak phyllosilicates is not uncommon. Consequently, the multidisciplinary approach commonly used to investigate fault zones may contribute to increase the understanding of landslide faulting processes and the assessment of their hazard potential.},
  language  = {en}
}
@article{SchuckJanssenSchleicheretal.2018,
  author    = {Schuck, Bernhard and Janssen, C. and Schleicher, Anja Maria and Toy, Virginia G. and Dresen, Georg},
  title     = {Microstructures imply cataclasis and authigenic mineral formation},
  series = {Journal of structural geology},
  volume    = {110},
  journal   = {Journal of structural geology},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0191-8141},
  doi       = {10.1016/j.jsg.2018.03.001},
  pages     = {172 -- 186},
  year      = {2018},
  abstract  = {The Alpine Fault is capable of generating large (MW > 8) earthquakes and is the main geohazard on South Island, NZ, and late in its 250-291-year seismic cycle. To minimize its hazard potential, it is indispensable to identify and understand the processes influencing the geomechanical behavior and strength-evolution of the fault. High-resolution microstructural, mineralogical and geochemical analyses of the Alpine Fault's core demonstrate wall rock fragmentation, assisted by mineral dissolution, and cementation resulting in the formation of a fine-grained principal slip zone (PSZ). A complex network of anastomosing and mutually cross-cutting calcite veins implies that faulting occurred during episodes of dilation, slip and sealing. Fluid-assisted dilatancy leads to a significant volume increase accommodated by vein formation in the fault core. Undeformed euhedral chlorite crystals and calcite veins that have cut footwall gravels demonstrate that these processes occurred very close to the Earth's surface. Microstructural evidence indicates that cataclastic processes dominate the deformation and we suggest that powder lubrication and grain rolling, particularly influenced by abundant nanoparticles, play a key role in the fault core's velocity-weakening behavior rather than frictional sliding. This is further supported by the absence of smectite, which is reasonable given recently measured geothermal gradients of more than 120 °C km-1 and the impermeable nature of the PSZ, which both limit the growth of this phase and restrict its stability to shallow depths. Our observations demonstrate that high-temperature fluids can influence authigenic mineral formation and thus control the fault's geomechanical behavior and the cyclic evolution of its strength.},
  language  = {en}
}
@misc{SchuckSchleicherJanssenetal.2020,
  author    = {Schuck, Bernhard and Schleicher, Anja Maria and Janssen, Christoph and Toy, Virginia G. and Dresen, Georg},
  title     = {Fault zone architecture of a large plate-bounding strike-slip fault},
  series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-51244},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-512441},
  pages     = {32},
  year      = {2020},
  abstract  = {New Zealand's Alpine Fault is a large, platebounding strike-slip fault, which ruptures in large (M-w > 8) earthquakes. We conducted field and laboratory analyses of fault rocks to assess its fault zone architecture. Results reveal that the Alpine Fault Zone has a complex geometry, comprising an anastomosing network of multiple slip planes that have accommodated different amounts of displacement. This contrasts with the previous perception of the Alpine Fault Zone, which assumes a single principal slip zone accommodated all displacement. This interpretation is supported by results of drilling projects and geophysical investigations. Furthermore, observations presented here show that the young, largely unconsolidated sediments that constitute the footwall at shallow depths have a significant influence on fault gouge rheological properties and structure.},
  language  = {en}
}
@article{SchuckSchleicherJanssenetal.2020,
  author    = {Schuck, Bernhard and Schleicher, Anja Maria and Janssen, Christoph and Toy, Virginia G. and Dresen, Georg},
  title     = {Fault zone architecture of a large plate-bounding strike-slip fault},
  series = {Solid Earth},
  volume    = {11},
  journal   = {Solid Earth},
  number    = {1},
  publisher = {Copernicus Publications},
  address   = {G{\"o}ttingen},
  issn      = {1869-9529},
  doi       = {10.5194/se-11-95-2020},
  pages     = {95 -- 124},
  year      = {2020},
  abstract  = {New Zealand's Alpine Fault is a large, platebounding strike-slip fault, which ruptures in large (M-w > 8) earthquakes. We conducted field and laboratory analyses of fault rocks to assess its fault zone architecture. Results reveal that the Alpine Fault Zone has a complex geometry, comprising an anastomosing network of multiple slip planes that have accommodated different amounts of displacement. This contrasts with the previous perception of the Alpine Fault Zone, which assumes a single principal slip zone accommodated all displacement. This interpretation is supported by results of drilling projects and geophysical investigations. Furthermore, observations presented here show that the young, largely unconsolidated sediments that constitute the footwall at shallow depths have a significant influence on fault gouge rheological properties and structure.},
  language  = {en}
}